In the reaction of copper with oxygen (O2), 800 g of copper (II) oxide was formed.

In the reaction of copper with oxygen (O2), 800 g of copper (II) oxide was formed. Calculate how much copper has reacted with oxygen? Сu + O2 → CuO

Reaction: 2Cu + O2 = 2CuO
Let’s find the amount of copper oxide substance: n = m / M = 800 g / (63.5 + 16) g / mol = 10.06 mol. According to the reaction, 2 mol of copper oxide was formed from 2 mol of copper, which means n (Cu) = n (CuO) = 10.06 mol. The mass of copper is m = n * M = 10.06 mol * 63.5 g / mol = 638.81 g (M is the molar mass determined according to the periodic table).
Answer: the mass of copper is 638.81 g.